Answer:
Most fish use gills for gas exchange instead of lungs.
Explanation:
False, muscle cells move the skeleton while nerve cells send electrical signals to the brain which tell the muscle cells to move
Some methods of determining the size of population are direct and indirect observations, sampling, and mark-and-recapture studies
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Sampling - Done by counting the animals in a small area and then estimating how many are in the larger area. You go out and take samples from different places so you can take the average. In most cases, it is not possible to count every member of a population so an estimate is made.
Mark and recapture - Another estimating method is a technique called "mark and recapture." This technique gets its name because some animals are first captured, marked, and released into the environment. Then another group of animals is captured. The number of marked animals in this second group indicates the population size.
Indirect observation - The members of a population may be small or hard to find. It may be easier to observe their tracks or other signs rather than the organisms themselves.
Direct observation - The most obvious way to determine the size of a population is to count, one by one.
The Hardy–Weinberg principle, also known as the Hardy–Weinberg equilibrium, model, theorem, or law, states that allele and genotype frequencies in a population will remain constant from generation to generation in the absence of other evolutionary influences.
